Various devices have been developed heretofore to measure the content of dissolved gases such as hydrogen in molten metals, such as molten aluminum or molten steel. An early device is described in U.S. Pat. No. 2,861,450 issued to Ransley et al. The device shown therein is referred to as the Telegas device. This device is included in an immersion head of generally a bell-shaped configuration and entails discharging or debouching a carrier gas into the molten metal and recapturing bubbles by the probe head. These devices entailed the recirculation of the gases through a closed loop until equilibrium is reached. The nitrogen reached an equilibrium with the dissolved hydrogen, which thus enables monitoring and measurement of the dissolved hydrogen content in the metal. These devices, as well as subsequent variations thereof, uses a membrane which is permeable to the gas, usually hydrogen, whose concentration is to be determined, but which is stated to be impermeable to molten metal. A need continues to exist for such probes which offer testing of increased speed and accuracy.